An equalizer is an important component in a communication system. Signal distortion and increase of data error rate usually occur due to multipath interference and the shadow effect caused by objects blocking a transmission path. An equalizer is therefore used for channel compensation to mitigate interference and noise caused by channel effects.
FIG. 1 depicts a diagram of a decision feedback equalizer 10 (DFE). The decision feedback equalizer 10 comprises a channel matching filter (CMF) 110, a feed-forward equalizer (FFE) 130, an inter-symbol interference removing unit (ISI) 150, a slicer 170 and a feedback equalizer (FBE) 190.
The decision feedback equalizer 10 receives a transmitted signal S0 from a transmitter, and signal-to-noise ratio (SNR) of the communication signal S0 is improved after the signal passes through the channel matching filter 110. The communication signal S0 then goes through the feed-forward equalizer 130, the inter-symbol interference removing unit 150 and the feedback equalizer 190 to eliminate the interference in the channel paths. Finally, the decision feedback equalizer 10 utilizes the slicer 170 for determining the received signal.
One drawback of the decision feedback equalizer 10 is that it may only remove the symbol interference of past data but not the interference of future data. And thus, for channels with great delay spread, the decision feedback equalizer 10 may be significantly influenced by the inter-symbol interference which causes high output data error rate.